Zach Pine invented his sand globe technique in 2000, and has taught over a thousand people how to make them. In five minutes you can learn the basic technique; it usually takes beginners about ten minutes to make a grapefruit-sized globe. The globes have an evocative "planetary" quality, the process of making them feels great, and we can use them in all sorts of creative ways (including throwing them to each other, and into the ocean).
In 2014, Zach started working on Earth in Your Hands, a worldwide sand globe project. He's also combined sand globe making with numerous beach habitat restoration/cleanup events.
See this gallery of sand globe photos, and this video of a sand globe event at Stinson beach.
Sand globes are made from sand and a little bit of water. The "glue" that holds the globe together is the intermolecular force that attracts water molecules to each other and to the grains of sand. When making the globes, we throw them in the air, and this causes liquifaction, similar to what happens to some areas of the earth during an earthquake. In this liquified airborne state, the globe seeks the lowest energy configuration: a sphere. See this NASA video of a water sphere in space to get an idea of the strength of attraction that water has to itself, and how that attraction causes a sphere to form.